Over the years there has been a continuing demand for a flexible, one-component, room temperature curing electrically conductive material for use in the electronic industry as electromagnetic shielding as well as for electrical grounding applications.
While various materials of the above type have been offered, the cost and performance thereof have been a major factor which has tended to limit the applications and/or use of the prior art materials.
Accordingly, a new and improved one-component room temperature curing electrically conductive material was needed which would not only provide consistently high performance but would also be saleable at relatively low cost.
In the prior art there is disclosed at least three basic classes of curing agent which have been used to prepare non-conductive one component, room temperature moisture curable silicone rubber.
These agents generally are classified as:
1. THE TITANIUM CURING OR CROSS-LINKING AGENTS SUCH AS SHOWN IN U.S. Pat. No. 3,334,067;
2. THE ORGANOSILOXANE ACYLOXY CURING OR CROSS-LINKING AGENTS SUCH AS REFERRED TO U.S. Pat. No. 3,277,047; and
3. THE AMINOSILANE OR AMINOSILAZANE CURING OR CROSS-LINKING AGENTS SUCH AS DISCLOSED IN U.S. Pat. No. 3,032,528 and German Pat. No. 1,120,690.
This invention is based at least in part upon the unexpected discovery that electrically conductive particles supporting an outer noble metal surface e.g., an insulating or dielectric core supporting an outer noble metal surface such as glass coated with silver when intermixed with a siloxane polymer and an amine curing vulcanizing or cross-linking agent such as disclosed in U.S. Pat. No. 3,032,528 which is incorporated herein by reference hereto (rather than a titanium or organo-silicon acyloxy curing agent) within certain limits and kept in an anhydrous state (away from moisture) will upon use and in the presence of moisture at room temperature cure to provide a highly electrically conductive flexible cured silicone rubber.
Applicant has discovered in attempts made to produce a product comparable to the present invention, that is by using siloxane polymer containing the aforementioned titanium or organo-silicon acyloxy curing agents, mechanical or electrically useless or comparatively unsuccessful shielding or grounding silicone rubber products are prepared.